Machine tools are usually adapted for being used with many different tool sets. A typical tool set includes a punch and a corresponding die, wherein a stripper plate is also commonly included as part of the tool set. In processing a workpiece (e.g., a piece of sheet metal), it is common to use several different tool sets. In some cases, once a first tool set has been used, it is exchanged for a second tool set, and then a third, and so on. Once a first workpiece has been fully processed using the desired sequence of tool sets, a second workpiece may be processed, in some cases beginning again with the first tool set.
The tool sets used on a machine tool are often stored in cartridges. Some cartridges may be stored in the machine tool, while others may be kept nearby. When several different tool sets (e.g., of different size and/or shape) are used for a job, the machine tool is commonly provided with cartridges respectively holding the different tool sets. Not only do the cartridges store the tools, they may also be used to facilitate loading and unloading the tools on the machine tool. For example, when it is desired to use a particular tool set, a cartridge holding that tool set is moved to a mounting position on the machine tool. At the mounting position, the tools are automatically removed from the cartridge and loaded onto the machine tool, with the die held in position by a corresponding die shoe. Once use of that tool set is finished, its tools are unloaded from the machine tool and loaded back onto the cartridge. The cartridge is then moved away from the mounting position. Then, a different cartridge (holding another tool set) can be moved to the mounting position so that a new set of tools can be used by the machine tool. This process is repeated for as many different tool sets as are needed for a given job. In some cases, the machine tool includes an elongated rail for storing the cartridges. The cartridges, for example, can be slidably engaged with the rail such that they can be slid back and forth to and from the mounting position. In other cases, the cartridges are stored in a rotary storage system, a round carousel, or a stacked storage system. The mounting and dismounting of tool sets using cartridges is described in U.S. Pat. No. 4,951,375. This '375 patent is incorporated herein by reference to the extent it shows and describes the structure of an exemplary machine tool with a cartridge guidance system.
As is known with such cartridges, a die is held therein via a die shoe, with the die shoe and corresponding die being simultaneously loaded onto the machine tool. As illustrated in FIGS. 1 and 2, a cartridge 10 is shown holding a die shoe 12, wherein the shoe 12 defines an inner recess 14 sized to accommodate a die 16, with the die shoe recess 14 having a outer surface 18 sized to mate with the outer side surface 20 of the die 16. The die 16 is often retained from rotation in the die shoe recess 14 via a key 22 of the die shoe 12. As shown, the key 22 has a portion 24 (e.g., an upper portion) that at least partially lies within the die shoe recess 14. As is known, dies (such as the die 16) are generally configured with a key channel 26 that extends vertically along the die outer side surface 20. Accordingly, upon being placed in a die shoe, such as the die shoe 12, the die 16 is positioned such that its vertical key channel 26 is aligned with the key 22. In turn, the key's upper portion 24 slides within the die's key channel 26 and, in turn, contacts side surfaces of the channel 26, thereby preventing rotation of the die 16 within the shoe 12.
One problem encountered to date with such above-described assembly between die shoe and die is further depicted in FIGS. 2-5. As is known, following sharpening processes of the die 16, the die 16 is normally brought back to its original height in the die shoe 12 with use of one or more shims 28 positioned between the die 16 and die shoe 12. With use of a limited amount of shims 28, as shown in FIG. 2, there often remains contact between the die outer side surface 20 and the recess outer surface 18 at key side 30 of the die shoe 12. However, with further sharpening of the die 16, and subsequently more shims 28 being positioned between the die 16 and shoe 12 (as illustrated in FIG. 3), portions of the die 16 are raised to heights 32 (as illustrated in FIG. 4) at which there is no longer appreciable contact between the die outer side surface 20 and the recess outer surface 18 at the key side 30 of the die shoe 12. Consequently, the die 16 can become ajar from the die shoe 12. As a result, the die 16 would be free to move laterally, with a likelihood that the die 16 (along with one or more of the shims 28 nearest the die 16) potentially slides out from the die shoe recess 14. Such event is depicted in FIG. 5, wherein the die 16 and shims 28 (collectively referenced as 34) are shown starting to slide laterally out of the recess 14, and coming into contact with the key's portion 24 within the die's key channel 26.
In light of the above, the outer surface 18 at the key side 30 of the die shoe 12, or key-side bearing surface of the shoe 12, is found to be the limiting factor for how much the die 16 can be sharpened and shimmed, while still being held in workable position in the shoe 12. To that end, in the case of loading a tool set in a machine tool from a cartridge, if such tool set involves a die shoe from which a die has become ajar, a machine sensor would be known to identify the situation and return an error message to the operator. Consequently, current cartridges can be used with dies only so long as sufficient retaining contact is made between the die shoe bearing surface and the dies. Unfortunately, this results in dies needing to be replaced in such die shoes before the dies' usable lives are reached.
Additionally, a problem can arise during use of dies within the die shoes, particularly following sharpening of such dies. For example, when a die is sharpened, its edges can often become jagged. Such jagged edges are often found to interfere with workpieces being slid across the die's upper surface, with the workpieces catching against the edges. Such catching, or contact between a workpiece and the die's surface, can result in compromising the machining process, which stems from improper positioning of the workpiece, and in some cases, the movement of the die, depending on size of the workpiece. As a consequence, material ends up being scrapped and time is lost in the process.
Accordingly, when using cartridges, issues can develop with both corresponding die shoes and dies used therein. The present invention addresses these and other problems.